The present invention generally relates to electrically powered pumps and more particularly relates to a motor-pump assembly.
German publication DE 196 32 167 A1 discloses a generic motor-pump aggregate which is suitable especially for electronically controlled brake systems of motor vehicles and comprises an electric motor with a holding plate, e.g. for contact brushes, and a piston pump, wherein pistons of the pump are drivable by means of an eccentric. In this publication, the pistons are respectively urged against the eccentric by means of a resetting spring and thus follow the eccentric""s movements.
It is generally known in the art, however, that a coupling ring which is connected to the pistons may be used instead of the resetting springs. In the event of e.g. two opposite pistons, one piston executes a pressure stroke movement due to the eccentric, while the other piston that is retracted by the coupling ring executes a suction stroke movement. This means that the coupling ring does not rotate along with the eccentric but oscillates. Twisting of the coupling ring may occur especially during start of the pump, and the coupling ring may push against stationary or rotating parts of the motor-pump aggregate, whereby undesirable noise and friction is caused in particular when contact with rotating parts takes place. Shavings and other small particles which are produced thereby will also impair the operability of the motor-pump aggregate.
In the international patent application assigned publication No. WO 00/13951, which was published only after the priority date of the present patent application, a stop formed fast with the housing is therefore provided on the side of the coupling ring opposite to the motor. On the other side which faces the motor, the coupling ring may get into contact with an equalizing substance rotating with the motor shaft or the eccentric or other rotating parts during operation so that increased wear and undesirable running noise is produced at this location.
In view of the above, an object of the present invention is to improve upon a motor-pump aggregate of the type referred to hereinabove so as to reduce running noise and friction by simple means.
According to the present invention, this object is achieved in that in a generic motor-pump aggregate a projection is additionally provided on the holding plate of the motor and extends into the range of motion of the coupling ring. This achieves a stationary stop for the coupling ring according to the present invention, and friction and possible running noises are thereby reduced. The fact that an existing component is modified also permits curtailing manufacturing costs, e.g., for a separate stop, as well as assembling costs and time.
The end of the projection itself can be used as a stop when the material has a suitable abrasive resistance. Alternatively, a separate stop or abutment for the coupling ring made from an appropriate material, e.g., sheet metal, may also be provided on the projection.
Preferably, the projection has a circular design and is arranged around the shaft of the motor which extends into the pump housing. Alternatively, the projection may also have individual segments which project into the range of motion of the coupling ring.
In motor-pump aggregates there is always the demand that the inside of the motor be free from foreign bodies. Contaminants could affect or damage the sensitive electronics of the motor, with the result of malfunction of the entire aggregate. On the one hand, these contaminants may be solid media such as dust or abraded parts. On the other hand, they also may be liquid media such as hydraulic fluid, especially brake fluid, of the pump and water or salt water that enters from the outside into the aggregate. To effectively separate the pump from the motor, a fire wall is therefore especially favorably arranged between the projection and the shaft and prevents or impedes the ingress of foreign media into the inside of the motor.
Advantageously, the fire wall can be designed integrally with the holding plate. But it is also possible that the fire wall is designed as an independent component part, e.g., integral with the separate stop.
Beside the function as a stop for the coupling ring, the projection of the holding plate which extends until into the range of motion of the coupling ring has another advantage. Leakage fluid of the pump always accumulates in the crank chamber, that means the space where the eccentric is arranged, during operation of the motor-pump aggregate. When an outlet channel for leakage fluid is provided in the housing of the pump, and especially an outlet means is arranged at the end of said channel remote from the eccentric or the crank chamber, the said fluid is allowed to discharge from the crank chamber outwards, for example, also into a controller housing in which an electronic control unit for the motor-pump aggregate can be accommodated in a fluid-tight fashion, that means, in any case isolated from the discharging leakage fluid. This drain satisfies the requirements when the motor-pump aggregate of the present invention is e.g. mounted into a motor vehicle in the manner shown in FIG. 1.
If, however, a vertical installation of the aggregate as described above is not possible, discharge of the leakage fluid is impeded. This problem exists in particular in the mounting position of the aggregate shown in FIG. 2 which is turned by 90xc2x0 compared to FIG. 1. To collect the leakage fluid, an indentation is then arranged especially advantageously in the housing at the outlet channel.
When the projection has a chamfer at the outside periphery of its end facing the indentation, leakage fluid can enter easily into the slot between projection or holding plate and pump housing. This is because, preferably, another channel for leakage fluid is provided between the projection or holding plate and the housing. Due to the fact that the projection extends into the range of motion of the coupling ring according to this invention, this further channel starts already at a point that is relatively remote from the motor so that the motor""s inside is better protected against the ingress of leakage fluid and other foreign bodies contained in the fluid.
When this further channel does not extend out of the pump housing, a reservoir for the leakage fluid may be provided between the pump housing and the holding plate in a favorable way for fluid collection. As an alternative, it is also possible to arrange a reservoir for leakage fluid in the motor compartment.